The Antarctic continent shows the most extreme environmental conditions. The stable temperatures of the Southern Ocean are at or near the freezing point of sea water. Although antarctic waters exhibit low seasonal variability in temperature, light, development of sea-ice and primary production show marked seasonal fluctuations. Thus the antarctic fauna is subject to extreme environmental conditions and exhibit particular adaptations. The major features of the biology of antarctic marine poikiloterms are low metabolism, seasonal growth rates, large yolky eggs and delayed maturity. Many authors also suggested that reproductive cycles appear to be closely linked to the primary production cycle The antarctic fauna is smaller and much less diverse on a higher taxonomic level (order, family) than might be expected given the considerable age and large area of the ecosystem. The shelf and slope waters are dominated both in therms of species and biomass by a single, endemic perciform suborder, the Notothenioidei. Some of the common characteristics of this suborder are: slow growth, prolonged gametogenesis, low fecundity and large yolky eggs. As in most vertebrates, reproduction in fish is a cyclic phenomenon, generally in Teleost fishes this periodicity is annual and it is influenciated by environmental changes. However, some antarctic species show a different pattern and exhibit uncoupled reproductive cycles. It is possible that there could be selective advantages to be gained by species that are able to be independent of the production cycle and thereby avoid large variations in breeding success from year-to-year changes in the environment. To a better understanding of the biology of fish living in the extreme conditions of marine polar environment it is of great interest the study of the antarctic fauna adaptations. Reproduction is a key parameter in the study of notothenioidei adaptations. Describing oogenesis stages and sexual maturation, spawning characteristics and fecundity, the life cycle of these species can be reconstructed, giving basis knowledge about their biology. The main objective of this project is to describe the characteristics of Notothenioiids reproductive cycle, its relation with environmental parameters and its intraspecific variation. Based in oogenesis histochemical analysis, reproductive parameters such as fecundity, spawning and seasonality were evaluated in 9 species belonging to the families Channichtyidae, Artedidraconidae, Harpagiferidae and Bathydraconidae (Pisces: Perciformes). Results reveal that the oocyte development events are very similar to those described for other notothenioids and for most other Teleost. Reproductive strategies in notothenioids differ mainly in the differential exploitation of temporal or spatial resources. Thus, these observations suggest that specialisation in Antarctic fish are more related to ecological diversification than to any kind of adaptation concerning oogenesis.